Data transmission method and apparatus in relay transmission type radio network

ABSTRACT

To provide a data transmission method and an apparatus thereof in a relay transmission type radio network capable of selecting an appropriate down-link relay route according to a location of a terminal station. A first relay node having received an up-link ACK packet transmitted by the terminal station transmits to an second relay node the up-link ACK packet including a source terminal station ID and a relay source node ID representing its own node ID. The second relay node having received the up-link ACK packet registers information on a pair of the source terminal station ID and the relay source node ID with a relay node list, and selects an appropriate route of a down-link packet addressed to the terminal station by using the information registered with the relay node list.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional under 37 C.F.R. § 1.53(b) Of priorapplication Ser. No. 10/010,530, filed Dec. 5, 2001, the entirety ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a data transmission method and anapparatus therefor in a relay transmission type radio network.

2. Description of the Related Art

FIG. 18 is a diagram illustrating a cell configuration of a conventionalcellular system. As for the cell configuration of this cellular system,it is comprised of cells 101 and base stations (nodes) 102, where aserviceable area is constituted by placing a plurality of cells as inFIG. 18. Each of nodes 102 is connected by a wire basic network 104 anda wire circuit 103, so that service signals such as voice and data andvarious control signals are communicated via these links. Moreover,there are cases where each of nodes 102 is connected to the wire basicnetwork 104 by providing concentration stations or the likehierarchically between them. A terminal station 105 performscommunication with the node 102, and transmits and receives varioussignals communicated by the wire basic network 104 and the wire circuit103. The wire basic network 104 has a server apparatus installed formanaging location information on the terminals and radio nodes, andperforming accounting and so on.

In order to cope with the increase in the number of subscribers to thecellular systems such as portable telephones and the Fixed WirelessAccess, a technique of reducing a cell radius to decrease a processingload per node is adopted. In the case of constructing the system withsuch minimal cells, a very large number of the nodes are placed so as tosecure a service area.

In addition, in the case where a high density data transmission systemsuch as multilevel modulation is applied in order to sup-linkporthigh-speed data transmission, the area covered by one node inevitablybecomes smaller to secure required received quality, and so a very largenumber of the nodes are also placed in this case.

Furthermore, while the cellular systems were mainly designed inquasi-micro and microwave zones in the past, construction of thecellular systems using quasi-millimeter and millimeter wave zones isexpected because of a crisis of frequency pressure. A higher frequencyweakens a diffraction effect and makes it markedly straight so that anunexpected call becomes difficult, which inevitably leads to a smallerarea covered by each node. To be more specific, a very large number ofthe nodes are also placed in such a case since a call area must besecured with the minimal cells.

In the case of constructing the systems with a large number of theminimal cells, it is essential to consolidate a wire network for thepurpose of connecting the node group-link to the basic network. Toconnect a very large number of the geographically unevenly distributednodes with the basic network, however, it is necessary to install thewire networks everywhere and so the cost of the entire system increases.Therefore, there is a technique of connecting the nodes by radio andperforming relay transmission so as to expand the service area.

FIG. 19 is a diagram illustrating an example of the cell configurationwherein relay nodes 204, 205 and 206 are placed around a core node 203connected to a wire network 201 by a wire circuit 202 and the relaynodes and the core node are connected by radio. A symbol 208 indicatesan example of an area covered by the node. The up-link packettransmitted from a terminal 207 reaches the core node 203 via the relaynodes 205 and 204, and then the packet received by the core node 203 iscommunicated to the wire network 201 by way of the wire circuit 202. Onthe other hand, the down-link packet to the terminal 207 sent from thewire network 201 is sent to the core node 203 first by way of the wirecircuit 202 and then is communicated from the core node 203 to theterminal 207 by way of the relay nodes 204 and 205.

In the case of transmitting the down-link packet in the cellconfiguration shown in FIG. 19, there was a challenge that theappropriate relay route must be selected out of a plurality of the relayroutes according to the location of the terminal 207, and that, if theterminal station moves, the relay route of the down-link packet to theterminal station must be changed as appropriate following the move.

SUMMARY OF THE INVENTION

Thus, an object of the present invention is to provide the datatransmission method and apparatus in a relay transmission type radionetwork capable of selecting the appropriate down-link relay routeaccording to the location of the terminal station.

Another object of the present invention is to provide the datatransmission method and apparatus in the relay transmission type radionetwork allowing the down-link relay route to be changed following themove of the terminal station and capable of selecting the down-linkrelay route appropriate to the above described move.

According to the first aspect of the present invention, a datatransmission method in a relay transmission type radio network includinga core node connected to a wire network, relay nodes relaying adown-link packet transmitted from said core node and an up-link packetdirected toward said core node and a terminal station capable oftransmission and reception of packet with both of said core node andsaid relay node, comprising:

a registration step for registering with a relay node list held by thenode, as a pair, ID information on said terminal station and a relaysource node included in the up-link packet transmitted by said terminalstation, in each of said core node and said relay node; and

a selection step for selecting a down-link relay route of the down-linkpacket addressed to said terminal station on the basis of said relaynode list, in each of said core node and said relay node.

According to the second aspect of the present invention, a relay noderelaying a down-link packet transmitted from a core node connected to awire network and an up-link packet directed toward said core node, andcapable of communication with a terminal station, comprising a relaynode list for having recorded ID information on said terminal stationand a relay source node included in the up-link packet directed towardsaid core node by said terminal station and giving a down-link relayroute of the down-link packet addressed to said terminal station on thebasis of said ID information.

According to the third aspect of the present invention, a core nodeconnected to a wire network, and capable of transmission and receptionof packet with both of a terminal station and a relay node, comprising arelay node list for having recorded ID information on said terminalstation and the relay node that is a relay source node included in areceived up-link packet and giving a down-link relay route of adown-link packet addressed to said terminal station on the basis of saidID information is provided.

According to the fourth aspect of the present invention, a terminalstation capable of transmission and reception of packet with both of acore node connected to a wire network and a relay node relaying adown-link packet transmitted from said core node and an up-link packetdirected toward said core node, setting ID information on a sourceterminal station registered with a relay node list of said core node orsaid relay node as a pair with ID information on a relay source node onsaid up-link packet and transmitting said up-link packet to a relaydestination node.

In the data transmission method according to the present invention, eachof the core node and the relay nodes has the relay node list for givingthe down-link relay route of the down-link packet addressed to theterminal station, and selects the appropriate down-link relay route forthe down-link packet addressed to the terminal station according to thelocation of the terminal station on the basis of the relay node list.

The relay node according to the present invention holds as the relaynode list the ID information on the terminal station and the relaysource node included in the up-link packet directed toward the core nodeby the terminal station and selects the appropriate down-link relayroute for the down-link packet addressed to the terminal station on thebasis of information on the up-link relay route according to the IDinformation of the relay node list.

The core node according to the present invention holds as the relay nodelist the ID information on the terminal station and the relay sourcenode included in the up-link packet transmitted by the terminal stationand received by way of the relay destination node, and selects theappropriate down-link relay route for the down-link packet addressed tothe terminal station on the basis of information on the up-link relayroute according to the ID information of the relay node list.

The terminal station according to the present invention transmits to therelay destination node the up-link packet including the ID informationon the source terminal station registered with the relay node list ofthe core node or the relay node as a pair with an ID number of the relaysource node. Thus, it becomes possible, in each of the core node and therelay nodes, to generate the relay node list used to select thedown-link relay route of the down-link packet addressed to the terminalstation, and thus selection of the appropriate down-link relay route forthe down-link packet is implemented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing how a terminal station havingreceived a broadcast packet sends back an up-link ACK packet in a datatransmission method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing a field configuration of thebroadcast packet in the data transmission method according to theembodiment of the present invention;

FIG. 3 is a schematic diagram showing a configuration of the ACK packetin the data transmission method according to the embodiment of thepresent invention;

FIG. 4 is a flowchart showing an up-link ACK packet procedure performedon each relay node and core node in the data transmission methodaccording to the embodiment of the present invention;

FIG. 5 is a diagram illustrating an example of the relay node list heldby the relay node in the data transmission method according to theembodiment of the present invention;

FIG. 6 is a diagram illustrating how the relay node list is generatedaccording to the embodiment of the present invention;

FIG. 7 is a diagram illustrating the relay node list generated by therelay node list generation procedure according to the embodiment of thepresent invention;

FIG. 8 is a diagram illustrating the relay node list generated by therelay node list generation procedure according to the embodiment of thepresent invention;

FIG. 9 is a diagram illustrating the relay node list generated by therelay node list generation procedure according to the embodiment of thepresent invention;

FIG. 10 is a diagram showing how the relay node list is generated in thecase where the terminal station has moved in the data transmissionmethod according to the embodiment of the present invention;

FIG. 11 is a diagram illustrating the relay node list that is generatedon the relay node in the case where the terminal station has moved inthe data transmission method according to the embodiment of the presentinvention;

FIG. 12 is a flowchart showing another example of the up-link ACK packetprocedure performed on each relay node and core node in the datatransmission method according to the embodiment of the presentinvention;

FIG. 13 is a diagram concretely illustrating how the relay node list isgenerated in the data transmission method according to the embodiment ofthe present invention;

FIG. 14 is a schematic diagram showing a configuration of an up-linkpacket in the data transmission method according to the embodiment ofthe present invention;

FIG. 15 is a schematic diagram showing a configuration of a down-linkpacket in the data transmission method according to the embodiment ofthe present invention;

FIG. 16 is a flowchart showing the relay and transmission process of thedown-link packet in the data transmission method according to theembodiment of the present invention;

FIG. 17 is a diagram concretely illustrating the down-link packet relayoperation in the data transmission method according to the embodiment ofthe present invention;

FIG. 18 is a diagram illustrating a cell configuration of a conventionalcellular system; and

FIG. 19 is a diagram illustrating an example of a cell configuration ofa radio relay type cellular system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described hereafter.

First, selection of a down-link relay route in this embodiment will bedescribed by using FIGS. 1, 2, 3 and 4. In this embodiment, a case wherea relay destination node (receiver side relay node) for each relay nodeto relay and transmit an up-link packet is already known is assumed. Tobe more specific, the case where the relay route of the up-link packetis given in advance is assumed. There are the cases where a directionalantenna is installed on each relay node and core node. There are thecases where the directional antenna is fixedly installed and where it isadaptably installed as to its directivity. Installing the directionalantenna cuts back interference given to surrounding nodes and theterminal station, whereby it becomes possible to achieve high linkcapacity in the entire system.

Each relay node and core node periodically transmits a broadcast packet,and there are the cases where the broadcast packet is transmitted withfixed transmitting power. Details of the broadcast packet and an up-linkACK packet are described later by using FIGS. 2 and 3. In FIG. 1, relaynodes F08, F12 and F09 periodically transmit the broadcast packet by wayof down-link radio circuits F02, F07 and F10 respectively. Each terminalstation receives the broadcast packets from a plurality of nodes, andselects the node having transmitted the broadcast packet of the highestreceived power or of the best received quality of the received broadcastpackets. Terminals F01, F13 and F11 in FIG. 1 select the relay nodesF08, F12 and F09 respectively. The terminals F01, F13 and F11 havingselected the above described relay nodes transmit the up-link ACKpackets to the relay nodes F08, F12 and F09 respectively. The up-linkACK packets transmitted from the terminals F01, F13 and F11 arecommunicated to a core node F05 by way of relay routes F03, F06 and F04respectively.

FIG. 2 is a schematic diagram showing a field configuration of thebroadcast packet according to the embodiment of the present invention.The broadcast packet is comprised of a field E02 showing a core node ID,a field E03 showing a relay node ID, a field E04 showing data and another field E01. In each of the relay nodes, the ID of the core node ofa cell to which the relay node belongs is set in the core node ID fieldE02. On the core node, its own node ID is set in the relay node ID fieldE03. Moreover, there are cases where the core node ID field E02 isexcluded. The other field E01 has a pilot signal, a packet ID and thelike set therein. There are cases where the order of the fields ischanged. There are also the cases where the other field E01 is dividedand placed.

FIG. 3 is a schematic diagram showing a configuration of the up-link ACKpacket that is a response signal in the case where the terminal stationaccording to the embodiment of the present invention receives thebroadcast packet. The up-link ACK packet is comprised of a field G02showing a relay destination node (receiver side relay node) ID, a fieldG03 showing a relay source node (sender side relay node) ID, a field G04showing a source terminal station ID, and an other field G01. Each ofthe relay nodes sets an up-link relay destination node ID as the relaydestination node ID, sets its own node ID as the relay source node ID,and sets the ID of the terminal station having transmitted the up-linkACK packet as the source terminal station ID. In the case where each ofthe terminal stations sends the up-link ACK packet, the terminal stationsets the information indicating that it has transmitted in the relaysource node ID field G03. It is also possible to simultaneously set aplurality of the relay destination node IDs in the relay destinationnode ID field G02. The other field G01 has a pilot, an up-link anddown-link link indicator, a packet ID, data and the like set therein.The order of the fields may change. The other field G01 may be dividedand placed.

FIG. 4 shows an up-link ACK packet procedure performed on each relaynode and the core node of the embodiment of the present invention. Eachnode detects arrival of the up-link ACK packet in a step H01, and itproceeds to a step H02 in the case where the up-link ACK packet isdetected, and it returns to the step H01 in the case where the up-linkACK packet is not detected. In the step H02, each node determineswhether the received up-link ACK packet is the packet being relayed orthe packet transmitted from the terminal station. Here, thedetermination is made by referring to the field G03 representing therelay source node included in the up-link ACK packet, and if informationset in the field G03 indicates anything other than the relay sourcenode, each node determines that the received up-link ACK packet is thepacket from the terminal station. In the case where it is determined tobe the up-link ACK packet from the terminal station in the step H02,each node transmits the up-link ACK packet to the relay destination nodeafter setting necessary information such as the relay source node ID ina step H05. In the case where the terminal station or the relay nodetransmits the up-link ACK packet, it may control the transmitting powerof the up-link ACK packet so as to meet predetermined received power orpredetermined received quality at a transmission destination node. It ispossible to cut back the interference and increase the link capacity bycontrolling the transmitting power of the up-link ACK packet. In thecase where it is determined to be the up-link ACK packet from the relaysource node in the step H02, each node refers to the relay destinationnode ID included in the up-link ACK packet in a step H03, and itproceeds to a step H04 if its own node ID is set in the field G02, orreturns to the step H01 if anything other than its own node ID is set inthe field G02. In the step H04, each node obtains the information on therelay source node ID and the source terminal station ID included in thereceived up-link ACK packet, and records their relationship on a relaynode list. In the case where the above described source terminal stationID is already registered with the relay node list, each node cancels theregistration and then registers the relay source node ID and the sourceterminal station ID of this time. If there is no change in therelationship between the relay source node ID and the source terminalstation ID, however, neither of them needs to be registered. Details ofthe relay node list will be described later by referring to FIG. 5.After registering it with the relay node list, each node transmits theup-link ACK packet to the relay destination node after setting necessaryinformation such as the relay source node ID in the step H05.

FIG. 5 is a diagram illustrating an example of the relay node list heldby the relay node according to the embodiment of the present invention.In FIG. 5, it describes the relationship between the node ID showing arelay destination node of a down link and a destination terminal stationID showing the terminal station receiving a down-link packet. Forinstance, in the case where a terminal station MS-3 is specified as thedestination terminal station of a certain down-link packet, the relaynode holding the relay node list of FIG. 5 transmits the receiveddown-link packet to a relay node BS-C. In the case where the node ID forthe terminal station is not registered on the relay node list on therelay node or the core node, it is regarded as the down-link packet sentto the terminal station. When registering a pair of new node ID andterminal station ID on the relay node list, in the case where theterminal station ID is already registered, the registration is canceledand then the pair of the new node ID and terminal station ID areregistered. However, in the case where, as a result of making an inquiryabout the relationship between the node ID and the terminal stationregistered on the relay node list, the same pair as the new node ID andterminal station ID are already registered, neither ID needs to beregistered. In the case where the pair of the node ID and the terminalstation ID on the relay node list is not up-linkdated or inquired aboutfor a fixed time or longer, the registration of the pair may be deleted.

FIG. 6 is a diagram illustrating how the relay node list according tothe embodiment of the present invention is generated. It is assumed thatthe up-link relay destination node is already known. In FIG. 6, relaynodes RN-1, RN-2, RN-3 and RN-4 are periodically transmitting thebroadcast packet respectively.

A terminal station MS-A receives the broadcast packet by way of a radiopropagation path I01, and selects the relay node RN-1 as a connectionnode. The terminal station MS-A transmits the up-link ACK packet to therelay node RN-1 by way of a radio propagation path I04. At this time,the up-link ACK packet has the ID “MS-A” set as the source terminalstation ID and the ID “RN-1” set as the relay destination node IDrespectively. The relay node RN-1 receives the up-link ACK packettransmitted from the terminal station MS-A, and then transmits theup-link ACK packet to the relay node RN-3 that is the up-link relaydestination node by way of a radio propagation path I02. At this time,the up-link ACK packet has the ID “RN-1” set as the relay source nodeID, the ID “MS-A” set as the source terminal station ID and the ID“RN-3” set as the relay destination node ID respectively. The relay nodeRN-3 refers to the relay source node ID “RN-1” and the source terminalstation ID “MS-A” included in the up-link ACK packet transmitted fromthe relay node RN-1 to register the pair of the node ID “RN-1” and theterminal station ID “MS-A” with the relay node list. The relay node RN-3transmits the up-link ACK packet received from the relay node RN-1 tothe relay node RN-4 that is the up-link relay destination node of therelay node RN-3 by way of a radio propagation path I03. At this time,the up-link ACK packet has the ID “MS-A” set as the source terminalstation ID, the ID “RN-3” set as the relay source node ID and the ID“RN-4” set as the relay destination node ID respectively. The relay nodeRN-4 receives the up-link ACK packet transmitted from the relay nodeRN-3 by way of the radio propagation path I03, and registers with therelay node list held by the relay node RN-4 the source terminal stationID “MS-A” and the relay source node ID “RN-3” included in the up-linkACK packet as a pair.

In FIG. 6, a terminal station MS-B receives the broadcast packet fromthe relay node RN-2 by way of a radio propagation path I09, and selectsthe relay node RN-2 as the connection node. The terminal station MS-Btransmits the up-link ACK packet to the relay node RN-2 by way of aradio propagation path I08. At this time, the up-link ACK packet has theID “MS-B” set as the source terminal station ID and the ID “RN-2” set asthe relay destination node ID respectively. The relay node RN-2 receivesthe up-link ACK packet transmitted from the terminal station MS-B, andthen transmits the up-link ACK packet to the relay node RN-3 that is theup-link relay destination node for the relay node RN-2 by way of a radiopropagation path I05. At this time, the up-link ACK packet has the ID“RN-2” set as the relay source node ID, the ID “MS-B” set as the sourceterminal station ID and the ID “RN-3” set as the relay destination nodeID respectively. The relay node RN-3 refers to the relay source node ID“RN-2” and the source terminal station ID “MS-B” included in the up-linkACK packet transmitted from the relay node RN-2 to register the pair ofthe node ID “RN-2” and the terminal station ID “MS-B” with the relaynode list held by the relay node RN-3. The relay node RN-3 transmits theup-link ACK packet received from the relay node RN-2 to the relay nodeRN-4 that is the up-link relay destination node of the relay node RN-3by way of the radio propagation path I03. At this time, the up-link ACKpacket has the ID “MS-B” set as the source terminal station ID, the ID“RN-3” set as the relay source node ID and the ID “RN-4” set as therelay destination node ID respectively. The relay node RN-4 receives theup-link ACK packet transmitted from the relay node RN-3 by way of theradio propagation path I03, and registers with the relay node list heldby the relay node RN-4 the source terminal station ID “MS-B” and therelay source node ID “RN-3” included in the up-link ACK packet as apair.

In FIG. 6, a terminal station MS-D receives the broadcast packet fromthe relay node RN-5 by way of a radio propagation path I12, and selectsthe relay node RN-5 as the connection node. The terminal station MS-Dtransmits the up-link ACK packet to the relay node RN-5 by way of aradio propagation path I11. At this time, the up-link ACK packet has theID “MS-D” set as the source terminal station ID and the ID “RN-5” set asthe relay destination node ID respectively. The relay node RN-5 receivesthe up-link ACK packet transmitted from the terminal station MS-D, andthen transmits the up-link ACK packet to the relay node RN-2 that is theup-link relay destination node for the relay node RN-5 by way of a radiopropagation path I10. At this time, the up-link ACK packet has the ID“RN-5” set as the relay source node ID, the ID “MS-D” set as the sourceterminal station ID and the ID “RN-2” set as the relay destination nodeID respectively.

The relay node RN-2 refers to the relay source node ID “RN-5” and thesource terminal station ID “MS-D” included in the up-link ACK packettransmitted from the relay node RN-5 to register the pair of the node ID“RN-5” and the terminal station ID “MS-D” with the relay node list heldby the relay node RN-2. The relay node RN-2 transmits the up-link ACKpacket received from the relay node RN-5 to the relay node RN-3 that isthe up-link relay destination node of the relay node RN-2 by way of theradio propagation path I05. At this time, the up-link ACK packet has theID “MS-D” set as the source terminal station ID, the ID “RN-2” set asthe relay source node ID and the ID “RN-3” set as the relay destinationnode ID respectively. The relay node RN-3 refers to the relay sourcenode ID “RN-2” and the source terminal station ID “MS-D” included in theup-link ACK packet transmitted from the relay node RN-2 to register thepair of the node ID “RN-2” and the terminal station ID “MS-D” with therelay node list held by the relay node RN-3. The relay node RN-3transmits the up-link ACK packet received from the relay node RN-2 tothe relay node RN-4 that is the up-link relay destination node of therelay node RN-3 by way of the radio propagation path I03. At this time,the up-link ACK packet has the ID “MS-D” set as the source terminalstation ID, the ID “RN-3” set as the relay source node ID and the ID“RN-4” set as the relay destination node ID respectively.

The relay node RN-4 receives the up-link ACK packet transmitted from therelay node RN-3 by way of the radio propagation path I03, and registerswith the relay node list held by the relay node RN-4 the source terminalstation ID “MS-D” and the relay source node ID “RN-3” included in theup-link ACK packet as a pair.

In FIG. 6, a terminal station MS-C receives the broadcast packet fromthe relay node RN-3 by way of a radio propagation path I06, and selectsthe relay node RN-3 as the connection node. The terminal station MS-Ctransmits the up-link ACK packet to the relay node RN-3 by way of aradio propagation path I07. At this time, the up-link ACK packet has theID “MS-C” set as the source terminal station ID and the ID “RN-3” set asthe relay destination node ID respectively. The relay node RN-3 receivesthe up-link ACK packet transmitted from the terminal station MS-C, andthen transmits the up-link ACK packet to the relay node RN-4 that is theup-link relay destination node for the relay node RN-3 by way of theradio propagation path I03. At this time, the up-link ACK packet has theID “RN-3” set as the relay source node ID, the ID “MS-C” set as thesource terminal station ID and the ID “RN-4” set as the relaydestination node ID respectively. The relay node RN-4 receives theup-link ACK packet transmitted from the relay node RN-3 by way of theradio propagation path I03, and registers with the relay node list heldby the relay node RN-4 the source terminal station ID “MS-C” and therelay source node ID “RN-3” included in the up-link ACK packet as apair.

FIG. 7 is a diagram illustrating the relay node list on the relay nodeRN-2 generated by the relay node list generation procedure described byusing FIG. 6. As shown in FIG. 7, the list indicating the down-linkrelay destination node to relay the down-link packet for each terminalstation is generated on the relay node RN-2 shown in FIG. 6, andaccordingly, selection of the down-link relay route for each terminalstation is autonomously implemented in the relay node RN-2.

FIG. 8 is a diagram illustrating the relay node list on the relay nodeRN-3 generated by the relay node list generation procedure described byusing FIG. 6. As shown in FIG. 8, the list indicating the down-linkrelay destination node to relay the down-link packet for each terminalstation is generated on the relay node RN-3 shown in FIG. 6, andaccordingly, selection of the down-link relay route for each terminalstation is autonomously implemented in the relay node RN-3.

FIG. 9 is a diagram illustrating the relay node list on the relay nodeRN-4 generated by the relay node list generation procedure described byusing FIG. 6. As shown in FIG. 9, the list indicating the down-linkrelay destination node to relay the down-link packet for each terminalstation is generated on the relay node RN-4 shown in FIG. 6, andaccordingly, selection of the down-link relay route for each terminalstation is automously implemented in the relay node RN-4.

Next, FIG. 10 is a diagram showing how the relay node list is generatedin the case where the terminal station MS-A in FIG. 6 has moved. FIG. 10shows the case where the terminal station MS-A moves from the areacovered by the relay node RN-1 to the area covered by the relay nodeRN-2.

In FIG. 10, the terminal station MS-A receives the broadcast packet fromthe relay node RN-2 by way of a radio propagation path I14, and selectsthe relay node RN-2 as the connection node. The terminal station MS-Atransmits the up-link ACK packet to the relay node RN-2 by way of aradio propagation path I13. At this time, the up-link ACK packet has theID “MS-A” set as the source terminal station ID and the ID “RN-2” set asthe relay destination node ID respectively. The relay node RN-2 receivesthe up-link ACK packet transmitted from the terminal station MS-A, andthen transmits the up-link ACK packet to the relay node RN-3 that is theup-link relay destination node for the relay node RN-2 by way of theradio propagation path I05. At this time, the up-link ACK packet has theID “RN-2” set as the relay source node ID, the ID “MS-A” set as thesource terminal station ID and the ID “RN-3” set as the relaydestination node ID respectively. The relay node RN-3 refers to therelay source node ID “RN-2” and the source terminal station ID “MS-A”included in the up-link ACK packet transmitted from the relay node RN-2to register the pair of the node ID “RN-2” and the terminal station ID“MS-A” with the relay node list held by the relay node RN-3. Here, whilethe terminal station MS-A pairing off with the relay node RN-1 isalready registered with the relay node list held by the relay node RN-3as shown in FIG. 8, the terminal station MS-A pairs off with the relaynode RN-2 this time, so that the relay node RN-3 changes it by deletingthe ID “MS-A” registered for the ID “RN-1” to newly have the ID “RN-2”and the ID “MS-A” as a pair. The relay node RN-3 transmits the up-linkACK packet received from the relay node RN-2 to the relay node RN-4 thatis the up-link relay destination node of the relay node RN-3 by way ofthe radio propagation path I03. At this time, the up-link ACK packet hasthe ID “MS-A” set as the source terminal station ID, the ID “RN-3” setas the relay source node ID and the ID “RN-4” set as the relaydestination node ID respectively. The relay node RN-4 receives theup-link ACK packet transmitted from the relay node RN-3 by way of theradio propagation path I03, and attempts to register with the relay nodelist held by the relay node RN-4 the source terminal station ID “MS-A”and the relay source node ID “RN-3” included in the up-link ACK packetas a pair. However, the relay node RN-4 does not need to newly registerit since the pair of the ID “MS-A” and the ID “RN-3” is alreadyregistered with the relay node list held by the relay node RN-4 as shownin FIG. 9.

FIG. 11 shows the relay node list that is generated on the relay nodeRN-3 in the case where the terminal station MS-A moves from the areacovered by the relay node RN-1 to the area covered by the relay nodeRN-2 as shown in FIG. 10. As shown in FIG. 11, the relay node RN-3 shownin FIG. 10 cancels the registration of the terminal station MS-A pairingoff with the relay node RN-1 and registers the ID “MS-A” so that itpairs off with the relay node RN-2. There are cases where cancellationof the terminal station MS-A pairing off with the relay node RN-1 isperformed after some time has elapsed. In this case, the two relayroutes by way of the relay nodes RN-1 and RN-2 is set to one terminalstation MS-A, which receives the packets from those two relay nodes RN-1and RN-2 so as to have the effect of site diversity.

As above, according to the embodiment of the present invention, it ispossible to adaptably select the down-link relay route even in the casewhere the terminal station has moved. The shorter a transmission cycleof the broadcast packet is, the faster move of the terminal station canbe the subject of implementation of the down-link relay route selection.

In addition, a radio relay type cellular network as a precondition hasthe effect of allowing more stable communication compared with an ad hocnetwork wherein a moving terminal serves concurrently as the relaycenter, since the relay nodes are deployed fixedly as infrastructure.

Moreover, it is feasible, by controlling the transmitting power of anup-link data packet or a down-link data packet, to cut back interferencegiven to the surrounding nodes and terminal stations, whereby itconsequently has the effect of allowing the link capacity in the entiresystem to be improved.

FIG. 12 is a flowchart showing another example of the up-link ACK packetprocedure performed on each relay node and core node according to theembodiment of the present invention. As shown in FIG. 12, each nodedetects arrival of the up-link ACK packet in a step D01, and it proceedsto a step D02 in the case where the up-link ACK packet is detected, andit returns to the step D01 in the case where the up-link ACK packet isnot detected. In the step D02, each node determines whether the receivedup-link ACK packet is the packet being relayed or the packet transmittedfrom the terminal station. Here, the determination is made by referringto the field G03 representing the relay source node included in the ACKpacket, and if information set in the field G03 indicates anything otherthan the relay source node, each node determines that the receivedup-link ACK packet is the packet from the terminal station. In the casewhere it is determined to be the up-link ACK packet from the terminalstation in the step D02, each node transmits the up-link ACK packet tothe relay destination node after setting necessary information such asthe relay source node ID in a step D06. In the case where the terminalstation or the relay node transmits the up-link ACK packet, it maycontrol the transmitting power of the up-link ACK packet so as to meetpredetermined received power or predetermined received quality at thetransmission destination node. It is possible to cut back theinterference and increase the link capacity by controlling thetransmitting power of the up-link ACK packet.

In the case where it is determined to be the up-link ACK packet from therelay source node in the step D02, each node refers to the relaydestination node ID included in the up-link ACK packet in a step D03,and it proceeds to a step D04 if its own node ID is set in the fieldG02, or returns to the step D01 if anything other than its own node IDis set in the field G02. In the step D04, each node obtains theinformation on the relay source node ID and the source terminal stationID included in the received up-link ACK packet, and determines whetheror not their relationship is already recorded with the relay node list.In the case where, in the step D04, it is determined that the pair ofthe relay source node ID and the source terminal station ID included inthe received up-link ACK packet is already registered, each node doesnot relay the packet and returns to the step D01. In the case where itis not registered, each node registers the relationship between therelay source node ID and the source terminal station ID with the relaynode list in a step D05. Here, in the case where the above describedsource terminal station ID is already registered with the relay nodelist, each node cancels the registration thereof and then registers thepair of the relay source node ID and the source terminal station ID ofthis time. After registering it with the relay node list in the stepD05, each node transmits the up-link ACK packet to the relay destinationnode after setting the necessary information such as the relay sourcenode ID in the step D06.

FIG. 13 is a diagram concretely illustrating how the relay node list isgenerated according to the up-link ACK packet procedure shown in FIG.12. In FIG. 13, placement of the terminal stations and relay nodes equalto that in FIG. 6 is assumed, and it represents a situation where theterminal stations MS-A, MS-B, MS-D and MS-C transmit or relay andtransmit the up-link ACK packets to the relay nodes RN-1, RN-2, RN-3,RN-4 and RN-5 respectively, and then the terminal station MS-B receivesthe broadcast packet to transmit the up-link ACK packet again. In FIG.13, the terminal station MS-B receives the broadcast packet from therelay node RN-2 by way of the radio propagation path I09, and selectsthe relay node RN-2 as the connection node. The terminal station MS-Btransmits the up-link ACK packet to the relay node RN-2 by way of theradio propagation path I08. At this time, the up-link ACK packet has theID “MS-B” set as the source terminal station ID and the ID “RN-2” set asthe relay destination node ID respectively. The relay node RN-2 receivesthe up-link ACK packet transmitted from the terminal station MS-B, andthen transmits the up-link ACK packet to the relay node RN-3 that is theup-link relay destination node for the relay node RN-2 by way of theradio propagation path I05. At this time, the up-link ACK packet has theID “RN-2” set as the relay source node ID, the ID “MS-B” set as thesource terminal station ID and the ID “RN-3” set as the relaydestination node ID respectively. The relay node RN-3 refers to therelay source node ID “RN-2” and the source terminal station ID “MS-B”included in the up-link ACK packet transmitted from the relay node RN-2to check whether or not the pair of the node ID “RN-2” and the terminalstation ID “MS-B” is already registered with the relay node list held bythe relay node RN-3.

As shown in FIG. 8, the pair of the ID “RN-2” and the ID “MS-B” isalready registered with the relay node list held by the relay node RN-3.And according to this example of relay node list generation, in the casewhere, as shown in FIG. 12, the pair of the relay source node ID and thesource terminal station ID included in the relayed and transmittedup-link ACK packet is already registered with the relay node list, therelay node RN-3 does not relay and transmit the up-link ACK packet tothe relay node (relay node RN-4) of higher order. Thus, it becomespossible to transmit the up-link ACK packet only in the case where therelay route needs to be changed, and traffic for transmitting theup-link ACK packet can be reduced, thus allowing the interference to becut back and the link capacity in the entire system to be improved.

Moreover, when generating the relay node list in the embodiment of thepresent invention, it is also possible to generate the relay node listwith the up-link packets other than the up-link ACK packet. Here, theup-link packets refer to up-link data packets transmitted by theterminal station, which are transmitted none the less whether or not thebroadcast packet is received.

FIG. 14 is a schematic diagram showing the configuration of the up-linkpacket. In FIG. 14, the up-link packet is comprised of a field 502showing the relay destination node ID, a field 503 showing the relaysource node ID, a field 504 showing the source terminal station ID andthe other field 501. In the relay node, the up-link relay destinationnode ID is set as the relay destination node ID, its own node ID is setas the relay source node ID, and the ID of the terminal station havingtransmitted the up-link packet is set as the source terminal station ID.In the case where the terminal station transmits the up-link packet, theterminal station sets the information, as the relay source node ID,indicating that the packet was transmitted by the station. It is alsopossible to simultaneously set a plurality of the relay destination nodeIDs in the field 502. The other field 501 has a pilot, an up-link anddown-link indicator, a packet ID, data and so on set. The order of thefields may change. The other field 501 may be divided and placed.

In FIGS. 4 and 12 showing the ACK packet procedure respectively, therelay node list is generated by replacing the portion equivalent to theup-link ACK packet with the up-link packet shown in FIG. 14.

Next, the down-link packet relay and transmission method according tothe embodiment of the present invention will be described. FIG. 15 is aschematic diagram showing the field configuration of the down-linkpacket. In FIG. 15, the down-link packet is comprised of a field 602showing the relay destination node ID, a field 603 showing the relaysource node ID, a field 604 showing the destination terminal station IDand the other field 601. In the case where a certain relay node relaysand transmits the down-link packet, the relay node determines the relaydestination node ID corresponding to the destination terminal station IDfrom the relay node list, and then sets the relay destination node ID inthe relay destination node ID field 602, sets the destination terminalstation ID in the destination terminal station ID field 604, and setsthe node ID of the relay node in the relay source node ID field 603. Inthe case where a certain relay node transmits the down-link packetdirectly to the terminal station, the relay node sets the informationdedicated to indication thereof in the relay destination node ID field602. The other field 601 has a pilot, an up-link and down-link linkindicator, a packet ID, data and so on stored. The order of the fieldsmay change. The other field 601 may be divided and placed.

FIG. 16 is a flowchart showing the relay transmission process of thedown-link packet shown in FIG. 15, and this process is one executed onthe core node and the relay node. In FIG. 16, each node detects arrivalof the down-link packet in a step S701, and it proceeds to a step S702if the down-link packet arrives, and it returns to the step 701 if thearrival of the packet is not detected. In the step S702, each nodedetermines whether or not the relay destination node ID included in thedown-link packet is its own node ID, and if its own node ID is set inthe field 602, it proceeds to a step S706, and if not, it returns to thestep S701. In the step S706, each node checks the destination terminalstation ID indicating the destination of the down-link packet, anddetermines whether or not the destination terminal station ID isincluded in the relay node list. In the case where the destinationterminal station ID is included in the relay node list, it proceeds to astep S703, and if the ID is not included therein, it proceeds to a stepS705. In the step S703, each node selects from the relay node list thenode ID to pair off with the destination terminal station, sets the nodeID as the relay destination node ID on the down-link packet. In a step704, each node transmits the down-link packet to the relay destinationnode selected in the step S703. Here, the down-link packet to be relayedand transmitted has its own node ID set as the relay source node ID andalso has the destination terminal station ID and the relayed data and soon set respectively. When the core node or the relay node transmits thedown-link packet, it may control the transmitting power of the down-linkpacket so as to meet predetermined received power or predeterminedreceived quality at a transmission destination node or terminal station.It is possible, by controlling the transmitting power of the down-linkpacket, to cut back the interference given to the surroundings, wherebyallowing high link utilization to be attained.

On the other hand, in the case where the destination terminal station IDis not included in the relay node list in the step S706, each nodetransmits the down-link packet directly to the terminal station in astep S705. At this time, the down-link packet has its own node ID set asthe relay source node ID and also has the information indicating thatthe down-link packet is transmitted to the terminal station set in therelay destination node ID field 602. In addition, the down-link packethas the destination terminal station ID, the down-link data and so onset respectively.

FIG. 17 is a diagram concretely illustrating the down-link packet relayoperation by the down-link packet relay transmission shown in FIG. 16.In FIG. 17, placement of the terminal stations and relay nodes that isthe same as FIG. 6 is assumed, and the relay node lists to the terminalstations MS-A, MS-B, MS-C and MS-D are already generated on the relaynodes RN-1, RN-2, RN-3 and RN-4. Now, the down-link packet sent to theterminal station MS-B arrives at the relay node RN-4. The relay nodeRN-4 refers to the relay node list shown in FIG. 9, and it grasps thatthe relay destination node to pair off with the terminal station MS-B isthe relay node RN-3. The relay node RN-4 relays the down-link packet tothe relay node RN-3. Here, the relay node RN-4 sets the ID “RN-4” as therelay source node ID, sets the ID “RN-3” as the relay destination nodeID, and sets the ID “MS-B” as the destination terminal station ID on thedown-link packet to be relayed. In addition, the other information(transmission data or the like) included in the down-link packet sent tothe terminal station MS-B having arrived at the relay node RN-4 is alsoset on the down-link packet. After the relay node RN-4 transmits thedown-link packet to the relay node RN-3 by way of a radio propagationpath 301, the relay node RN-3 receives the down-link packet. The relaynode RN-3 checks the destination terminal station of the down-linkpacket transmitted from the relay node RN-4, and checks whether or notthe terminal station is included in the relay node list held by therelay node RN-3 shown in FIG. 8. As the terminal station MS-B pairs offwith the relay node RN-2 as shown in FIG. 8, the relay node RN-3transmits the down-link packet to the relay node RN-2 just as in thecase where the relay node RN-4 relayed and transmitted the down-linkpacket to the relay node RN-3. The relay node RN-2 likewise checkswhether or not the terminal station MS-B is registered with the relaynode list held by the relay node RN-2 shown in FIG. 7. As the ID “MS-B”that is the ID of the destination terminal station MS-B is notregistered with the relay node list held by the relay node RN-2 as shownin FIG. 7, the relay node RN-2 determines that the terminal station MS-Bbelongs to the area of its own node, and transmits the down-link packetto the terminal station MS-B. At this time, on the down-link packet tobe sent to the terminal station MS-B, the relay node RN-2 sets the ID“RN-2” as the relay source node ID, sets the information dedicated tothe indication of transmission to the terminal station in the relaydestination node ID field 602, and sets the ID “MS-B” as the destinationterminal station ID. In addition, the relay node RN-2 also sets a datasignal or the like included in the down-link packet received by therelay node RN-2 on the down-link packet as appropriate.

The terminal station MS-B receives the down-link packet from the relaynode RN-2, confirms that it is the packet sent to its own terminal andthen demodulates the data.

As above, according to the embodiment of the present invention, it ispossible to adaptably select the down-link relay route even in the casewhere the terminal station has moved. The shorter the transmission cycleof the broadcast packet is, the faster move of the terminal station canbe the subject of implementation of the down-link relay route selection.

In addition, a radio relay type cellular network as a precondition hasthe effect of allowing more stable communication compared with the adhoc network wherein the moving terminal serves concurrently as the relaycenter, since the relay nodes are deployed fixedly as infrastructure.

Moreover, it is feasible, by controlling the sending power of theup-link data packet or the down-link data packet, to cut backinterference given to the surrounding nodes and terminal stations,whereby it consequently has the effect of allowing the link capacity inthe entire system to be improved.

According to the present invention, the information on the relay routeof the up-link packet is held as the relay node list on the core nodeand the relay node, and the relay route of the down-link packet isselected based on the above described information recorded on the relaynode list, so that it has the advantage of allowing selection of theappropriate down-link relay route according to the location of theterminal and further allowing selection of the down-link relay route tobe automously implemented in each of the relay nodes.

In addition, the present invention has the effect that, in the casewhere the terminal station moves, the relay route of the down-linkpacket to the terminal station can be changed as appropriate followingthe move.

1. A data transmission method in a relay transmission type radio networkincluding a core node connected to a wire network, relay nodes relayinga down-link packet transmitted from said core node and an up-link packetdirected toward said core node and a terminal station capable oftransmission and reception of packet with both of said core node andsaid relay node, comprising: a registration step for registering with arelay node list held by the node, as a pair, the terminal station ID anda relay source node ID, which is used as a relay destination node ID inthe case of sending packets to said terminal station, included in theup-link packet transmitted by said terminal station, in each of saidcore node and said relay node; and a selection step for selecting adown-link relay route of the down-link packet addressed to said terminalstation on the basis of said relay node list, in each of said core nodeand said relay node.
 2. The data transmission method according to claim1, comprising: a step for periodically transmitting a broadcast packetto said terminal station in each of said core node and said relay node;a connection node determination step for receiving said broadcast packetand determining a connection node out of said core node and said relaynode in said terminal station; a step for transmitting to saidconnection node an up-link ACK packet, as said up-link packet, includingthe ID information on said terminal station and directed toward saidcore node following a predetermined up-link relay route in said terminalstation; and a step for, in each of said relay nodes, setting on saidreceived up-link ACK packet the ID information on the relay node as theID information on said relay source node and transmitting it to a relaydestination node.
 3. A relay node relaying a down-link packettransmitted from a core node connected to a wire network and an up-linkpacket directed toward said core node, and capable of communication witha terminal station, comprising a relay node list for having recorded IDinformation on said terminal station and a relay source node included inthe up-link packet directed toward said core node by said terminalstation and giving a down-link relay route of the down-link packetaddressed to said terminal station on the basis of said ID information.4. A core node connected to a wire network, and capable of transmissionand reception of packet with both of a terminal station and a relaynode, comprising a relay node list for having recorded ID information onsaid terminal station and the relay node that is a relay source nodeincluded in a received up-link packet and giving a down-link relay routeof a down-link packet addressed to said terminal station on the basis ofsaid ID information is provided.
 5. A terminal station capable oftransmission and reception of packet with both of a core node connectedto a wire network and a relay node relaying a down-link packettransmitted from said core node and an up-link packet directed towardsaid core node, setting ID information on a source terminal stationregistered with a relay node list of said core node or said relay nodeas a pair with ID information on a relay source node on said up-linkpacket and transmitting said up-link packet to a relay destination node.